The present invention relates to a glass coated with a heat reflecting colored film and a process for its production.
In recent years, it has become common to employ a heat reflecting glass having a low solar energy transmittance (a ratio of directly transmitting energy to incident solar energy) as a means to increase cooling efficiency of e.g. a vehicle such as an automobile. As a method to reduce the solar energy transmittance, a method of employing a colored glass or a method of coating a colored film which is excellent in the heat reflecting performance on a transparent soda lime glass or on a colored glass having a high transmittance, is available. The latter method is preferred from the viewpoint of the heat reflecting performance and recycling of the glass.
What are required for such a glass coated with a heat reflecting colored film, may, for example, be that the solar energy transmittance is low, the visible light transmittance is high as compared with the solar energy transmittance, it has sufficient durability for use for e.g. vehicles, it has a color tone which does not impair the design of e.g. vehicles, and it has a high sheet resistance. As a glass coated with a heat reflecting colored film which satisfies these requirements, a glass is known wherein an oxide film comprising cobalt oxide as the main component, at least 10 mass % (the ratio based on the total metal amount, the same applies hereinafter) of iron and at least 5 mass % of chromium, is formed in a thickness of from 10 to 50 nm by a spraying method.
However, such a glass has had a problem such that the film thickness, composition, etc. are non-uniform, and the yield is poor.
It is known in literatures to obtain, by a sputtering method, a glass having a film formed which comprises cobalt oxide as the main component and at least 5 mass % of iron oxide. For example, JP-A-9-30837 discloses a heat reflecting glass having a coating film of metal oxides formed with a metal composition such that cobalt: 65 to 96 mass %, chromium: 2 to 25 mass %, iron: 2 to 33 mass %; and a sputtering method is mentioned as a method for forming such a coating film.
However, in a magnetron sputtering method whereby the film-forming speed is remarkably higher than the conventional methods, which is suitable for a mass production of a film having uniform film thickness and composition and which is a sputtering method presently utilized industrially, an alloy target comprising cobalt and iron can not be practically used, since such an alloy target is a ferromagnetic material, whereby a magnetic flux of magnetron is hardly formed over the target surface. In the above publication, no specific disclosure is given with respect to a sputtering method, and only a spraying method is specifically described.
Heretofore, it has been common that a ceramic paste having a ceramic color composition formed into a paste, is screen-printed along the peripheral portion or the center portion of a window glass of an automobile, followed by drying and baking in a bending step. Such a ceramic color paste is baked e.g. along the peripheral portion of glass to form a colored opaque layer and thereby to be used for preventing deterioration of an adhesive by ultraviolet rays or to prevent the bonded portion from being seen through from outside the car. As such a ceramic color composition, one having a heat resistant coloring pigment mixed to a glass frit, is known and usually has a color tone of a black color or a dark gray color. Such a composition is called a black ceramic coating material.
However, when such a ceramic color paste is printed on a glass having formed by a spray method a conventional oxide film comprising cobalt oxide as the main component, at least 10 mass % of iron and at least 5 mass % of chromium, there has been a problem that unfavorable whitish coloration is likely to result.
Further, when a glass is used as e.g. a rear glass of an automobile, so-called silver printing is carried out, wherein a silver paste which is an exothermic material to prevent fogging, is linearly printed and baked. However, a conventional glass having formed by a spray method an oxide film comprising cobalt oxide as the main component, at least 10 mass % of iron and at least 5 mass % of chromium, has had a problem that coloration of this silver print is poor (such that it forms an antique red color).
Accordingly, the above-mentioned glass coated with a heat reflecting colored film, cannot practically be produced by means of a magnetron sputtering method, and the above-mentioned problems such as formation of non-uniformity in the case of the production by the above-mentioned spray method, unfavorable whitish coloration in ceramic color printing, and poor coloration of silver printing, have not been solved.
It is an object of the present invention to provide a glass coated with a heat reflecting colored film, which can be produced by a sputtering method, which is excellent in the uniformity of the film thickness and composition and which is excellent in heat reflectivity, and a process for its production. Further, it is another object of the present invention to provide a glass coated with a heat reflecting colored film, which is excellent in the uniformity of the film thickness and composition, which is free from unfavorable whitish coloration in ceramic color printing and which is excellent in coloration of silver printing.
As a result of an extensive research, the present inventors have found that 1) a glass coated with a heat reflecting colored film, which comprises a glass substrate, and a specific first layer and a specific second layer, laminated sequentially by a sputtering method on one side of the glass substrate, is excellent in the uniformity of the film thickness and composition and excellent in the heat reflectivity, and that 2) a glass coated with a heat reflecting colored film obtained by heat treatment of such glass coated with a heat reflecting colored film, not only satisfies the basic required characteristics such that the solar energy transmittance is low, the visible light transmittance is higher than the solar energy transmittance, it has adequate durability for e.g. a vehicle, it has a color tone which does not impair the design for e.g. a vehicle, and the sheet resistance is high, but also is excellent in the uniformity of the film thickness and composition, free from unfavorable whitish coloration in ceramic color printing and excellent in coloration of silver printing, and thus have accomplished the present invention.
The present invention provides a glass coated with a heat reflecting colored film (hereinafter referred to also as xe2x80x9cglass A coated with a heat reflecting colored filmxe2x80x9d), which comprises a glass substrate, and a first layer containing iron oxide and a second layer containing cobalt oxide, laminated sequentially by a sputtering method on one side of the glass substrate, wherein:
in the first layer, the amount of iron based on the total metal amount is at least 60 mass %, and
in the second layer, the amount of cobalt based on the total metal amount is at least 60 mass %.
Further, the present invention provides a glass coated with a heat reflecting colored film (hereinafter referred to also as xe2x80x9cglass B coated with a heat reflecting colored filmxe2x80x9d), which comprises a glass substrate, and a first layer containing cobalt oxide and a second layer containing iron oxide, laminated sequentially by a sputtering method on one side of the glass substrate, wherein:
in the first layer, the amount of cobalt based on the total metal amount is at least 60 mass %, and
in the second layer, the amount of iron based on the total metal amount is at least 60 mass %.
Further, the present invention provides a glass coated with a heat reflecting colored film (hereinafter referred to also as xe2x80x9cglass C coated with a heat reflecting colored filmxe2x80x9d), which comprises a glass substrate, and a first layer containing iron oxide, chromium oxide and nickel oxide and a second layer containing cobalt oxide, laminated sequentially by a sputtering method on one side of the glass substrate, wherein:
in the first layer, the amounts of iron, chromium and nickel, based on the total metal amount, are as follows:
iron: from 60 mass % to 85 mass %,
chromium: from 10 mass % to 28 mass %, and
nickel: from 5 mass % to 24 mass %, and
in the second layer, the amount of cobalt based on the total metal amount is at least 60 mass %.
Further, the present invention provides a glass coated with a heat reflecting colored film (hereinafter referred to also as xe2x80x9cglass D coated with a heat reflecting colored filmxe2x80x9d), which comprises a glass substrate, and a first layer containing cobalt oxide and a second layer containing iron oxide, chromium oxide and nickel oxide, laminated sequentially by a sputtering method on one side of the glass substrate, wherein:
in the first layer, the amount of cobalt based on the total metal amount, is at least 60 mass %, and
in the second layer, the amounts of iron, chromium and nickel, based on the total metal amount, are as follows:
iron: from 60 mass % to 85 mass %,
chromium: from 10 mass % to 28 mass %, and
nickel: from 5 mass % to 24 mass %.
Further, the present invention provides a process for producing the above-mentioned glass A coated with a heat reflecting colored film, which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal oxide target containing iron oxide, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas.
Further, the present invention provides a process for producing the above-mentioned glass B coated with a heat reflecting colored film, which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal oxide target containing iron oxide.
Further, the present invention provides process for producing the above-mentioned glass C coated with a heat reflecting colored film, which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal target containing iron, chromium and nickel as components in a sputtering gas atmosphere containing an oxidizing gas, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas.
Further, the present invention provides a process for producing the above-mentioned glass D coated with a heat reflecting colored film, which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal target containing iron, chromium and nickel as components in a sputtering gas atmosphere containing an oxidizing gas.
Further, the present invention provides a glass coated with a heat reflecting colored film (hereinafter referred to also as xe2x80x9cglass E coated with a heat reflecting colored filmxe2x80x9d, obtained by heat treatment of the above-mentioned glass A, B, C or D coated with a heat reflecting colored film.
The above-mentioned glass E coated with a heat reflecting colored film is preferably such that the surface sheet resistance of the film-coated side is at least 105 xcexa9/xe2x96xa1.
The above-mentioned glass E coated with a heat reflecting colored film is preferably such that the visible light transmittance is from 20 to 40%, and the visible light reflectance of the film-coated side and the other side is from 20 to 40% and from 10 to 25%, respectively.
Further, the present invention provides a process for producing the above-mentioned glass E coated with a heat reflecting colored film, which comprises:
a step of coating a ceramic color paste and/or a silver paste on the above-mentioned glass A, B, C or D coated with a heat reflecting colored film obtained by the process as defined in any one of the above-mentioned processes, and
a step of then carrying out heat treatment.
Now, the present invention will be described in detail.
Each of glasses A, B, C and D coated with a heat reflecting colored film of the present invention, is a glass coated with a heat reflecting colored film, which comprises a glass substrate, and a specific first layer and a specific second layer, laminated sequentially by a sputtering method on one side of the glass substrate. Now, glasses A, B, C and D coated with a heat reflecting colored film of the present invention, will be described.
The glass substrate to be used for glasses A, B, C and D coated with a heat reflecting colored film of the present invention, is not particularly limited, and a commonly widely employed colorless transparent soda lime glass, a heat absorbing glass colored green, bronze, gray or the like, or a glass having a heat absorbing/ultraviolet absorbing property, may, for example, be employed. The first layer of glass A coated with a heat reflecting colored film, contains iron oxide. In the present invention, in addition to iron oxide, chromium oxide, nickel oxide, niobium oxide, molybdenum oxide, manganese oxide, silicon oxide, copper oxide, vanadium oxide, zinc oxide, zirconium oxide, carbon, etc., may be contained within the range of the following composition.
In the first layer of glass A coated with a heat reflecting colored film, the amount of iron based on the total metal amount is at least 60 mass %. The upper limit value is not particularly limited, and it may be used at most 100%. With a view to reducing the solar energy transmittance, it is preferably used in an amount of at least 90%, particularly at least 97%.
The thickness of the first layer of glass A coated with a heat reflecting colored film, can be selected depending upon the desired optical characteristics. For example, the thickness of the first layer is preferably adjusted to be from 3 to 15 nm, in a case where the visible light transmittance of the glass coated with a heat reflecting colored film of the present invention is made to be from 20 to 40%, and the visible light reflectance of the film-coated side and the other side is made to be from 20 to 40% and from 10 to 25%, respectively.
The second layer of glass A coated with a heat reflecting colored film, contains cobalt oxide. In the present invention, in addition to the cobalt oxide, niobium oxide, molybdenum oxide, manganese oxide, silicon oxide, copper oxide, vanadium oxide, zinc oxide, zirconium oxide, carbon, etc., may be contained within the range of the following composition.
In the second layer of glass A coated with a heat reflecting colored film, the amount of cobalt based on the total metal amount, is at least 60 mass %. The upper limit value is not particularly limited, and it may be used in an amount of at most 100%. With a view to reducing the solar energy transmittance, it is preferably used in an amount of at least 90%, particularly at least 97%.
The thickness of the second layer of glass A coated with heat reflecting colored film, can be selected depending upon the desired optical characteristics. For example, the thickness of the second layer is preferably adjusted to be from 10 to 50 nm, in a case where the visible light transmittance of the glass coated with a heat reflecting colored film of the present invention is made to be from 20 to 40%, and the visible light reflectance of the film-coated side and the other side is made to be from 20 to 40% and from 10 to 25%, respectively.
With respect to the composition, the preferred thickness, etc., the first layer of glass B coated with a heat reflecting colored film, is similar to the second layer of the above-mentioned glass A coated with a heat reflecting colored film.
With respect to the composition, the preferred thickness, etc., the second layer of glass B coated with a heat reflecting colored film, is similar to the first layer of the above-mentioned glass A coated with a heat reflecting colored film.
The first layer of glass C coated with a heat reflecting colored film, contains iron oxide, chromium oxide and nickel oxide. In the present invention, in addition to these oxides, niobium oxide, molybdenum oxide, manganese oxide, silicon oxide, copper oxide, vanadium oxide, zinc oxide, zirconium oxide, carbon, etc., may be contained with the range of the following composition.
From the viewpoint of the heat reflectivity and efficiency in the film formed by a magnetron sputtering method, in the first layer of glass C coated with a heat reflecting colored film, the amounts of iron, chromium and nickel, based on the total metal amount, are such that iron: from 60 mass % to 85 mass %, chromium: from 10 mass % to 28 mass %, and nickel: from 5 mass % to 24 mass %.
The thickness of the first layer of glass C coated with a heat reflecting colored film, can be selected depending upon the desired optical characteristics. For example, the thickness of the first layer is preferably adjusted to be from 3 to 15 nm, in a case where the visible light transmittance of the glass coated with a heat reflecting colored film of the present invention is made to be from 20 to 40%, and the visible light reflectance of the film-coated side and the other side is made to be from 20 to 40% and from 10 to 25%, respectively.
With respect to the composition, the preferred thickness, etc., the second layer of glass C coated with a heat reflecting colored film, is similar to the second layer of the above-mentioned glass A coated with a heat reflecting colored film.
With respect to the composition, the preferred thickness, etc., the first layer of glass D coated with a heat reflecting colored film, is similar to the second layer of the above-mentioned glass C coated with a heat reflecting colored film.
With respect to the composition, the preferred thickness, etc., the second layer of glass D coated with a heat reflecting colored film, is similar to the first layer of the above-mentioned glass C coated with a heat reflecting colored film.
Further, in the present invention, for the purpose of e.g. improving the durability or changing the reflectance, a functional layer to accomplish such an object may be provided on the second layer, between the first layer and the glass substrate, or on the side opposite to the side coated with the heat reflecting colored film.
As such a functional layer, a layer made of at least one element selected from the group consisting of silicon, titanium, zinc, tin, copper, zirconium, manganese, niobium and aluminum, or an oxide or nitride of such an element, may be mentioned.
The glass coated with a heat reflecting colored film of the present invention, has a film construction which can be formed by a sputtering method, whereby it is excellent in the uniformity of the film thickness and composition.
In the processes for producing glasses A, B, C and D coated with a heat reflecting colored film of the present invention, the above-described first layer and the above-described second layer may be sequentially laminated by a sputtering method on one side of the above-mentioned glass substrate, but they are particularly preferably carried out as follows, in that conventional sputtering targets can thereby be employed. It should be understood that the following processes are preferred embodiments, and the processes for producing glasses A, B, C and D coated with a heat reflecting colored film of the present invention, are not limited thereto.
(1) In the Case of Glass A Coated with a Heat Reflecting Colored Film
Glass A coated with a heat reflecting colored film is produced by a process which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal oxide target containing iron oxide, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas.
As the metal oxide target to be used in the step of laminating the first layer, one containing iron oxide, is used. Particularly preferred is one which contains iron oxide in an amount of from 60 to 100 mass % as the amount of iron based on the total metal amount, in order to bring the composition of the first layer as described above.
The sputtering gas may be one containing no oxidizing gas or may be one containing an oxidizing gas.
The sputtering gas containing no oxidizing gas may, for example, be an inert gas such as helium, neon, argon, krypton or xenon. Among them, argon is preferred from the viewpoint of the economical efficiency and ease of discharge. These inert gases may be used alone or in combination as a mixture of two or more of them.
The oxidizing gas may, for example, be oxygen or ozone, or it may be a gas mixture of oxygen and ozone. As the sputtering gas containing an oxidizing gas, a gas mixture of such an oxidizing gas and the above-mentioned inert gas, may be employed.
For the sputtering, a magnetron sputtering apparatus which is excellent in the film forming speed, etc., is usually employed. However, a sputtering apparatus of a type wherein no magnetic field is used, may also be employed.
Further, as the power source, any of a direct current power source, a power source for applying an electric power in pulses, an alternate current power source and a high frequency power source, may be employed.
As the target to be used for the step of laminating the second layer, a metal target containing cobalt, or a metal oxide target containing cobalt oxide, is used. Particularly, in order to adjust the composition of the second layer as described above, when a metal target containing cobalt is employed, it preferably contains cobalt in an amount of from 60 to 100 mass %, and when a metal oxide target containing cobalt oxide is employed, it preferably contains cobalt oxide in an amount of from 60 to 100 mass % as the amount of cobalt based on the total metal amount.
As the sputtering gas, one containing an oxidizing gas is employed in the case where a metal target containing cobalt is employed. As the oxidizing gas, the above-mentioned one may be employed.
In a case where a metal oxide target containing cobalt oxide is employed, the sputtering gas may be one containing no oxidizing gas, or one containing an oxidizing gas. As such an oxidizing gas, the above-mentioned one may also be employed.
When either target is employed, a gas mixture comprising an oxidizing gas and an inert gas, may be employed.
The sputtering apparatus is the same as in the case of the process of laminating the first layer.
(2) In the Case of Glass B Coated with a Heat Reflecting Colored Film
Glass B coated with a heat reflecting colored film is produced by a process which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal oxide target containing iron oxide.
The metal target, the sputtering gas and the sputtering apparatus to be used in the step of laminating the first layer, are the same as in the case of the second layer in process (1).
The metal target, the sputtering gas and the sputtering apparatus to be used in the step of laminating the second layer, are the same as in the case of the first layer in process (1).
(3) In the Case of Glass C Coated with a Heat Reflecting Colored Film
Glass C coated with a heat reflecting colored film, is produced by a process which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal target containing iron, chromium and nickel as components in a sputtering gas atmosphere containing an oxidizing gas, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas.
The metal target to be used in the step of laminating the first layer is not particularly limited with respect to the composition or structure. Among iron, chromium and nickel, two or more metals may form a single crystal phase or may be in the form of a solid solution. Otherwise, crystalline phases or non-crystalline phases of the above two or more metals may be present in a mixed state, or masses of the above two or more metals may be separately present, respectively. In the present invention, as the metal target, a metal target containing iron, chromium and nickel as components, is used from the viewpoint of discharge. Particularly in order to adjust the composition of the first layer a described above, one having the following composition is preferred:
Iron: from 63 to 78 mass %,
Chromium: from 16 to 24 mass %, and
Nickel: from 6 to 13 mass %.
For example, a non-magnetic stainless steel, more specifically, an austenite type non-magnetic stainless steel as stipulated in JIS G4304-1987, may be mentioned. Particularly preferred is SUS304.
As a preferred example for the target to be used in the step of laminating the second layer, a Co target or a Co3O4 target may be mentioned.
As the sputtering gas, one containing an oxidizing gas is employed. The oxidizing gas is as described above. Further, a gas mixture comprising an oxidizing gas and an inert gas may be employed.
The apparatus to be used for the sputtering is the same as in the case of the first layer in process (1).
The step of laminating the second layer is the same as in the case of process (1).
(4) In the Case of Glass D Coated with a Heat Reflecting Colored Film
Glass D coated with a heat reflecting colored film is produced by a process which comprises:
a step of laminating the first layer on one side of the glass substrate, by sputtering by means of a metal target containing cobalt in a sputtering gas atmosphere containing an oxidizing gas, or by sputtering by means of a metal oxide target containing cobalt oxide in a sputtering gas atmosphere containing no oxidizing gas or in a sputtering gas atmosphere containing an oxidizing gas, and
a step of laminating the second layer on the first layer, by sputtering by means of a metal target containing iron, chromium and nickel as components in a sputtering gas atmosphere containing an oxidizing gas.
The metal target, the sputtering gas and the sputtering apparatus to be used in the process of laminating the first layer, are the same as in the case of the second layer in process (3).
The metal target, the sputtering gas and the sputtering apparatus to be used in the step of laminating the second layer, are the same as in the case of the first layer in process (3).
Glasses A, B, C and D coated with a heat reflecting colored film of the present invention are excellent in the heat reflectivity. Specifically, the solar energy transmittance is preferably smaller than the visible light transmittance, particularly preferably at most 40% (more preferably at most 35%).
As described in the foregoing, glasses A, B, C and D coated with a heat reflecting colored film of the present invention are excellent in the uniformity of the film thickness and composition, since they can be produced by a sputtering method. Further, they exhibit excellent heat reflectivity. Further, as described hereinafter, glasses A, B, C and D coated with a heat reflecting colored film of the present invention, are suitably employed for the production of glass E coated with a heat reflecting colored film of the present invention.
Now, glass E coated with a heat reflecting colored glass of the present invention will be described.
The glass coated with a heat reflecting colored film of the present invention can be obtained by heat treatment of the above-mentioned glass A, B, C or D coated with a heat reflecting colored film.
By the heat treatment, the surface sheet resistance of the film-coated side will be improved, and the surface sheet resistance of the film-coated side will be preferably at least 105 xcexa9/xe2x96xa1, whereby the radio wave transmittance will be improved. Accordingly, it is suitably employed for vehicles or buildings.
Further, by the heat treatment, visible light reflectance of the film-coated side is decreased, preferably to a level of from 20 to 40%, which is a value suitable for vehicles.
The heat treatment is not particularly limited, and the conditions may be changed depending upon the desired optical characteristics. As a preferred specific example, heat treatment may be mentioned which is carried out at a temperature of from 500 to 700xc2x0 C. for from 3 to 5 minutes in an atmosphere containing oxygen (such as the atmospheric air).
Glass E coated with a heat reflecting colored film of the present invention is suitably employed for e.g. vehicles such as automobiles. The glass to be used for e.g. vehicles such as automobiles, is subjected to heat treatment in the atmosphere at a temperature of from 630 to 690xc2x0 C. or higher for from 3 to 7 minutes in the case of bending treatment. Accordingly, glass E coated with a heat reflecting colored film of the present invention may be obtained by subjecting glass A, B, C or D coated with a heat reflecting colored film to bending treatment and by utilizing the heat treatment at that time.
Further, when silver printing or printing by means of a ceramic color paste such as a black ceramic coating material, is applied to glass A, B, C or D coated with a heat reflecting colored film of the present invention, heat treatment (baking) is carried out in the atmosphere at a temperature of from 630 to 690xc2x0 C. or higher for from about 3 to 7 minutes. Accordingly, glass E coated with a heat reflecting colored film of the present invention may also be obtained by applying silver printing or printing by means of a ceramic color paste to glass A, B, C or D coated with a heat reflecting colored film and utilizing the heat treatment (baking) at that time.
Further, the bending treatment and silver printing or printing by means of a ceramic color paste, may be carried out simultaneously, and heat treatment at that time may be utilized.
Namely, the process for producing glass E coated with a heat reflecting colored film of the present invention may preferably be a process which comprises:
a step of coating a ceramic color paste and/or a silver paste on glass A, B, C or D coated with a heat reflecting colored film obtained by any one of the above-mentioned processes (1) to (4), and
a step of then carrying out heat treatment.
Coating of the ceramic color paste and/or the silver paste can be carried out by a usual method. For example, a screen printing method by means of a screen printing machine may be mentioned. In a case where both the ceramic color paste and the silver paste are to be coated, they may be separately coated or may be simultaneously coated.
The conditions for the heat treatment may be the same as in the case where they are not coated.
The ceramic color paste may, for example, be one containing crystalline glass frit (and/or non-crystalline glass frit), a heat resistant coloring pigment and a refractory filler. The ceramic color paste may, for example, be prepared by uniformly mixing the crystalline glass frit (and/or the non-crystalline glass frit), the heat resistant coloring pigment and the refractory filler in an organic vehicle and adjusting the mixture to a viscosity suitable for coating.
As the silver paste, one having fine silver particles and glass frit uniformly mixed to an organic vehicle, is adjusted to a viscosity suitable for coating.
Glass E coated with a heat reflecting colored film of the present invention, is excellent in the heat reflectivity. Specifically, the solar energy transmittance is preferably smaller than the visible light transmittance, particularly preferably at most 40% (more preferably at most 35%).
Glass E coated with a heat reflecting colored film of the present invention preferably has a surface sheet resistance of at least 105 xcexa9/xe2x96xa1 on the film-coated side. If the surface sheet resistance is within the above range, it is possible to secure adequate transmittance of radio waves of e.g. radios, televisions, mobile phones or car phones in e.g. vehicles such as automobiles.
Further, when glass E coated with a heat reflecting colored film of the present invention is employed as a rear window glass of an automobile, the surface sheet resistance on the film-coated side is preferably at least 106 xcexa9/xe2x96xa1.
Glass E coated with a heat reflecting colored film of the present invention is preferably such that the visible light transmittance is from 20 to 40%, and the visible light reflectance on the film-coated side and the other side is from 20 to 40% and from 10 to 25%, respectively. Within the above ranges, glass E is suitable for application to e.g. automobiles.
Glass E coated with a heat reflecting colored film of the present invention is excellent in the uniformity of the film thickness and composition as compared with one prepared by a conventional spray method, since the colored film is formed by a sputtering method.
As is different from a conventional glass having formed by a spray method an oxide film comprising cobalt oxide as the main component, at least 10 mass % of iron and at least 5 mass % of chromium, glass E coated with a heat reflecting colored film of the present invention is free from whitening or color forming failure when printing is applied by means of a ceramic color paste such as black ceramic coating material, although the reason is not clearly understood. Further, as is different from a conventional glass having formed by a spray method an oxide film comprising cobalt oxide as the main component, at least 10 mass % of iron and at least 5 mass % of chromium, glass E coated with a heat reflecting colored film is excellent in coloration of silver printing, although the reason is not clearly understood.
Applications of glass E coated with a heat reflecting colored film of the present invention are not particularly limited, but, for example, applications for vehicles such as automobiles, or for buildings, may be mentioned.
Further, the glass coated with a heat reflecting colored film of the present invention may be made into a laminated glass or a composite glass.
Glass E coated with a heat reflecting colored film of the present invention is useful for various applications, since not only it satisfies the basic required characteristics, but also it is excellent in the uniformity of the film thickness and composition, free from unfavorable whitish coloration in ceramic color printing and also excellent in coloration of silver printing.